Evidence for Magnetic Polarons in Hole-Doped Cobalt Perovskites

Conference · Fri Jan 01 04:00:00 EST 2010

OSTI ID:984386

Podlesnyak, Andrey A ^[1]; Furrer, Albert ^[2]; Straessle, Thierry ^[2]; Pomjakushina, Ekaterina ^[3]; Conder, Kazimierz ^[3]; Khomskii, D. I. ^[4]

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1. ORNL
2. Laboratory for Neutron Scattering ETHZ & PSI
3. Paul Scherrer Institut, Villigen, Switzerland
4. Universitat zu Koln, Koln, Germany

A substitution of La{sup 3+} by Sr{sup 2+} induces holes in the low-spin ground state of LaCoO{sub 3}, which behave as magnetic impurities with a very high spin value. In this work, we elucidate the mechanism of how already the light hole-doping x {approx} 0.002 dramatically affects magnetic properties of La{sub 1-x}Sr{sub x}CoO{sub 3}. Using inelastic neutron scattering data, obtained with and without external magnetic field, we find that the charges introduced by strontium doping do not remain localized at the Co{sup 4+} sites. Instead, each hole is extended over the neighboring Co{sup 3+} ions, transforming them to higher spin state and thereby forming a magnetic seven-site (heptamer) polaron. Spin-state polarons behave like magnetic nanoparticles embedded in an insulating nonmagnetic matrix. Lightly doped La{sub 1-x}Sr{sub x}CoO{sub 3} is a natural analog to artificial structures composed of ferromagnetic particles in insulating matrices.

• Research Organization: Oak Ridge National Laboratory (ORNL); Spallation Neutron Source
• Sponsoring Organization: SC USDOE - Office of Science (SC)
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 984386
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
COBALT
GROUND STATES
IMPURITIES
MAGNETIC FIELDS
MAGNETIC PROPERTIES
MATRICES
NEUTRONS
PEROVSKITES
POLARONS
SCATTERING
SPIN
STRONTIUM